Ruby on Rails: How to handle exceptions(rescue?) - ruby-on-rails

Question

I'm fetching videos' data from youtube, including general video info, and likes number of them.
The problem is that sometimes, there is no corresponding data. Maybe the video is private, or the likes number is 0.
In either case, there will report NoMethodError: undefined method 'likes' for nil:NilClass
How can I handle this? I just want to ignore them and continue to the next youtube video.
I think I can use something like rescue, but I don't find many tutorial of it.
Here is my code:
client = YouTubeIt::Client.new(:dev_key => my_key)
Video.all.each do |video|
video_info = client.video_by(video.url)
like_number = video_info.rating.likes.to_i
video.likes = like_number
if video.save
puts "#{video.title} likes: #{video.likes}"
end
end

Answer 1

Rather that using the exception handling, which is slower, in this case just check for the presence of the value before calling the method.
Assuming the error is generated on the line
like_number = video_info.rating.likes.to_i
simply use
client = YouTubeIt::Client.new(:dev_key => my_key)
Video.all.each do |video|
video_info = client.video_by(video.url)
# here check for the presence.
if video_info.rating
like_number = video_info.rating.likes.to_i
video.likes = like_number
if video.save
puts "#{video.title} likes: #{video.likes}"
end
end
end

Answer 2

You should check for all possible nil values with, eg, video.nil? and corresponding conditionals. Rescuing should always be your last resort (it's slow and dirty), but, if there is no way to predict where the script will fail, you can always rescue some piece of code:
begin
#your error-prone code
rescue
#action you want to take in case your error-prone code raises error
end
Here is a good article on exceptions: http://www.tutorialspoint.com/ruby/ruby_exceptions.htm.

Answer 3

In this example, the method body acts as default begin block so need of begin block
def any_method
client = YouTubeIt::Client.new(:dev_key => my_key)
Video.all.each do |video|
video_info = client.video_by(video.url)
# try tries to find the method, if not found returns nil
like_number = video_info.try(:rating).try(:likes).to_i
video.likes = like_number
if video.save
puts "#{video.title} likes: #{video.likes}"
end
end
# For any type of standard errors, use rescue block
rescue => error_object
p 'Sorry, some error occured'
p error_object
end